ci: Skip integration tests for fork PRs (#629)

## Summary

- Add `if` condition to the `integration_tests` job in the reusable
`_tests.yaml` workflow
- Integration tests now only run when the PR originates from the `apify`
org or on pushes to `master`
- This aligns with how the SDK handles it and prevents failing
integration tests on fork PRs (which lack access to secrets)

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: vdusek

.github/workflows/_tests.yaml

@@ -24,6 +24,11 @@ jobs:
 
   integration_tests:
     name: Integration tests
+    if: >-
+      ${{
+        (github.event_name == 'pull_request' && github.event.pull_request.head.repo.owner.login == 'apify') ||
+        (github.event_name == 'push' && github.ref == 'refs/heads/master')
+      }}
     uses: apify/workflows/.github/workflows/python_integration_tests.yaml@main
     secrets: inherit
     with: